1. Field of Invention
The present invention relates to a fan. More particularly, the present invention relates to a centrifugal fan.
2. Description of Related Art
Electric apparatuses, such as notebook computers, generate heat when operating. If the heat is not dissipated efficiently, the electric apparatuses may malfunction. In serious situations, the heat may damage electric elements in the electric apparatuses. Furthermore, burning electric elements may hurt users. One method for reducing the heat in electric apparatuses involves the use of centrifugal fans therein. Each centrifugal fan may include impellers and a driving device. Heat generated by operation of the electric elements may be dissipated by airflow generated by the centrifugal fans.
Known technology related to centrifugal fans used to solve the problem of poor air convection in the narrow hollow chamber of a notebook computer involves utilizing the shape of the housing to produce high pressure and rotation speed. However, Blade Pass Frequency (BPF) noise is produced by the centrifugal fan when wake flow is produced as a result of the blades hitting the tongue-shaped areas of the housing.
Recently, a ring-shaped centrifugal fan is used to reduce BPF noise. However, such a ring-shaped centrifugal fan needs to be improved to further reduce BPF noise and to realize greater airflow.
Therefore, there is a need to develop a centrifugal fan that can avoid the foregoing disadvantages.